As a process for exhibiting a stereoscopic effect by accentuating a main subject among subjects included in an image, there is performed processing of focusing the main subject and intentionally blurring the foreground and the background of the focused main subject. Also, stereoscopic video signals for realizing stereoscopic display might cause a problem that when a viewer attends to a distant view in the image, the viewer has a strong feeling of fatigue or cannot stereoscopically view the image (see Non-Patent Literature 1, for example). In order to prevent this problem, there is performed processing for blurring the distant view represented by stereoscopic video signals so as not cause the viewer attend to the distant view.
Also, in order to reduce the collective redundancy to improve the compression coding efficiency, there is performed image coding processing by collecting a number of pixels to form blocks. Accordingly, prediction coding is performed to improve the compression rate with use of the correlation between the blocks. Specifically, while inter prediction or intra prediction is performed on complicated images in units of small blocks, inter prediction or intra prediction is performed on smooth images in units of large blocks. This enables performance of efficient prediction on both complicated images and smooth images.
Patent Literature 1 discloses an ultrasonic diagnostic device, as a conventional example of a coding device for changing the block size based on characteristics of each of coding target regions of an image. Generally, according to such an ultrasonic diagnostic device, as a subject is closer to a focus point, an image resolution is higher, and as the subject is more distant from the focus point, the image resolution is lower. Accordingly, the ultrasonic diagnostic device determines the block size with use of distance information and focus point information, thereby achieving both high image quality of a region having a high resolution and high compression of a region having a low resolution.
Also, Patent Literature 2 discloses another conventional example of a coding device. Focusing an attention on that flicker tends to occur in a static region having a high flatness degree, the art of Patent Literature 2 increases the block size of such a static region having a high flatness degree so as to generate a compressed image with suppressed flicker.